Technical Abstract:
Emissions and availability of nutrients from manure depends on activities of resident microorganisms; however, the effects of diet, animal genetics or treatments on the microbial ecology of pig manure is largely unknown. Stainless steel tanks with total manure capacity of 900 L were designed to allow for continual addition of swine feces and urine, modeling dynamic on-farm manure storage systems. A 13-week experiment was conducted to determine when manure microbial populations in the tanks stabilized. Pigs were adapted to standard corn-soybean meal based diets for at least six weeks and assigned to one of twelve tanks (three pigs per tank). Each pig was housed in a metabolism crate for four to five weeks with total feces and urine collected twice daily and placed in respective tanks. Samples were taken on weeks 1, 5, 9 and 13 for enumeration of bacteria and denaturant gradient gel electrophoresis (DGGE) analysis. Total anaerobes and aerobes were determined by spiral platting dilutions onto reduced Wilkens-Chalgren agar and Nutrient agar, respectively, incubated at 37 degrees C and colonies enumerated automatically, with data transformation to log counts for statistical analysis. Total DNA was extracted from samples and the 16S rRNA gene V3-region was amplified prior to DGGE analysis. Numbers of total anaerobes decreased from 8.02 log colony forming units (CFU)/ml on week one to an average of 6.91 log CFU/ml on weeks 5, 9 and 13. Total aerobes decrease from 7.25 log CFU/ml week one to 6.23 log CFU/ml week five and averaged 5.41 log CFU/ml on weeks 9 and 13. Microbial community diversity as determine by DGGE was similar among tanks at weeks 5, 9 and 13; tank-to-tank variability in banding patterns was evident in week one. By week five, two dominant bands were noted in all tanks. Based on these data, tanks required nine weeks for manure stabilization.